Conventionally, an ultrasonic flaw inspection method is known as a method of nondestructively inspecting a structural member of an aircraft or the like. As a specific example, a damage length measurement system which can measure a length of damage, such as delamination or peeling, in an adhesive part or a bonded part, using an actuator which emits ultrasonic waves toward a region to be inspected and an FBG (fiber Bragg grating) sensor for receiving ultrasonic reflected waves reflected in the region to be inspected has been proposed (for example, refer to Japanese Patent Application Publication JP 2011-185921 A and Japanese Patent Application Publication JP 2014-194379 A).
In ultrasonic testing, it is important to enable to detect damage in a range to be tested more certainly.
Thus, an object of the present invention is to enable to nondestructively detect damage of a test target more certainly.